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Masked Duck | Nomonyx dominicus
Maskerstekelstaart | Pato enmascarado
The Masked Duck is a small, secretive stiff-tailed duck of densely vegetated freshwater marshes in the lowlands. It lives hidden among floating and emergent plants and, when disturbed, dives or slips away into the vegetation, so it is often overlooked even where it occurs. In the guide area it is scarce and unpredictable everywhere.
Voice
Usually silent. In display the male gives a soft, repeated oo-oo-oo and a rolling series of notes; the female a short clucking sound.
Recording: Fernando Igor de Godoy — CC BY-NC-SA 4.0 · converted to mono · xeno-canto
Identification
30–36 cm, compact, with a long, stiff tail that is often cocked. The breeding male is rufous with black spots on the back and flanks and a black mask from the forehead to behind the eye; the bill is bright blue with a dark tip. Females, juveniles and non-breeding males are brown with pale scaling and have two dark lines across the pale face: one through the eye and one across the cheek. In flight it shows a white wing patch in every plumage. It takes off straight from the water, without a run.
Confusion species
Ruddy Duck Oxyura jamaicensis is slightly larger. The male has a white cheek and a black cap instead of a black mask; the female has one dark cheek line instead of two. Ruddy Duck has no white in the wing and needs a run across the water to take off. Least Grebe Tachybaptus dominicus also lives on vegetated ponds, but has a thin bill, a yellow eye and no stiff tail.
Habitat
Freshwater marshes and ponds with abundant floating and emergent vegetation, such as water hyacinth and cattail, rice fields, flooded grassland and swamp forest; mainly in the lowlands. It dives for seeds and roots of aquatic plants and for small aquatic animals. The nest is well hidden in dense marsh vegetation or in a rice field.
Where the bird is most at home, classified by the vegetation units of Mexico and Central America.
Range and movements
Scattered and local in the lowlands of the guide area: on the Gulf side from Tamaulipas through Veracruz to Tabasco and Campeche, on the Pacific side in Jalisco, Colima and Oaxaca among other places, and further in Belize, Guatemala, Honduras, Nicaragua, Costa Rica and Panama. The species appears and disappears as wetlands fill and dry out, and numbers are small. Outside the guide area from southern Texas through the West Indies and South America to northern Argentina.
- Resident
- Summer visitor (c. Apr–Sep)
- Winter visitor (c. Oct–Mar)
- Passage (Mar–Apr, Oct–Nov)
- dark = core range, pale = thinly spread
How and when to look
Rarely seen; the best chances are at the edges of densely vegetated freshwater marshes and rice fields, preferably early in the morning or late in the afternoon, when birds sometimes come out onto open water. In Costa Rica Palo Verde and Caño Negro produce regular records, in Panama the marshes around Tocumen. After a period of heavy rain, newly formed marshes can suddenly hold birds.
Conservation status
Not threatened globally. Scarce and local in the guide area, and hard to monitor because of its secretive habits. The drainage of freshwater marshes is the main threat.
Scientific name
Nomonyx dominicus | (Linnaeus, 1766)
Linnaeus described the species in 1766 as Anas dominica; because it was later moved to another genus, the author and year stand in brackets. The genus Nomonyx was introduced in 1880 by Ridgway. Nomonyx is Greek, from nomos 'customary' and onux 'nail', after the distinctive shape of the nail at the bill tip. dominicus means 'of Santo Domingo', the old name for Hispaniola. The specimen the first description was based on came from Hispaniola (Santo Domingo).